Gas generating system

ABSTRACT

A gas generating system for use in an inflatable vehicle occupant protection system is provided wherein an end closure is coupled to an outer housing at a first end, in a metal-to-metal seal. The gas generating system may also include a baffle system having a plurality of flow orifices defining a flow path for generated gases through an interior of the gas generating system, and a plurality of particulate aggregation surfaces positioned along the flow path of the gases for changing a flow direction of gases impinging on the aggregation surfaces. Each aggregation surface of the plurality of aggregation surfaces is oriented such that a difference between a flow direction of the gases prior to impinging on the aggregation surface and a flow direction of the gases after impinging on the aggregation surface is at least approximately 90°, wherein particulates in gases impinging on the aggregation surfaces aggregate on the surfaces.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of provisional application Ser. No.60/686,906, filed on Jun. 2, 2005.

BACKGROUND OF THE INVENTION

The present invention relates generally to gas generating systems and,more particularly, to filterless gas generating systems for use inapplications such as inflatable occupant restraint systems in motorvehicles.

Installation of inflatable occupant protection systems as standardequipment in all new vehicles has intensified the search for smaller,lighter and less expensive protection systems. Accordingly, since theinflation gas generator used in such protection systems tends to be theheaviest and most expensive component, there is a need for a lighter,more compact, and less expensive gas generating system.

A typical gas generating system includes cylindrical steel or aluminumhousing having a diameter and length related to the vehicle applicationand characteristics of a gas generant composition contained therein.Because inhalation by a vehicle occupant of particulates generated bygas generant combustion during airbag activation can be hazardous, it isdesirable to remove particulate material, or slag, produced duringcombustion of the gas generant. Thus, the gas generating system isgenerally provided with an internal or external filter comprising one ormore layers of steel screen of varying mesh and wire diameter. Gasproduced upon combustion of the gas generant passes through the filterbefore exiting the gas generating system. In a conventional system, theparticulates are substantially removed as the gas passes through thefilter. In addition, heat from combustion gases is transferred to thematerial of the filter as the gases flow through the filter. Thus, aswell as filtering particulates from the gases, the filter acts to coolthe combustion gases prior to dispersal into an associated airbag.However, inclusion of the filter in the gas generating system increasesthe complexity, weight, and expense of the gas generating system. Thus,a gas generating system construction which removes particulates andcools the generated gases without the need for a filter is desirable.

Variations in the filter components and in the arrangement of the filtermaterial can also unpredictably and adversely affect gas flow throughthe filter, thereby contributing to ballistic variability of the gasgenerating system and making the system response less predictable.

Yet another concern involves reducing the size of the inflator therebyreducing the packaging size and providing greater design flexibility invarious applications or uses. Furthermore, reducing the size of theinflator reduces the raw material requirements, and may alsoadvantageously reduce the manufacturing complexity, thereby reducingoverall manufacturing costs.

Other ongoing concerns with gas generating systems include the abilityto achieve any one of a variety of ballistic profiles by varying as fewof the physical parameters of the gas generating system as possibleand/or by varying these physical parameters as economically as possible.

SUMMARY OF THE INVENTION

The above-referenced concerns may be mitigated or obviated by providinga gas generating system for use in an inflatable vehicle occupantprotection system, a system that may if desired be filterless. In oneaspect, the gas generating system includes a baffle system having aplurality of flow orifices defining a flow path for generated gasesthrough an interior of the gas generating system, and a plurality ofparticulate aggregation surfaces positioned along the flow path of thegases for changing a flow direction of gases impinging on theaggregation surfaces. Each aggregation surface is oriented such that adifference between a flow direction of the gases prior to impinging onthe aggregation surface and a flow direction of the gases afterimpinging on the aggregation surface is at least approximately 90°,wherein particulates in gases impinging on the aggregation surfacesaggregate or collect on the surfaces.

In another aspect of the invention, the gas generating system includesan outer housing including a combustion chamber, a baffle system, andmay also include a high gas-yield, low solids-producing gas generantcomposition positioned in the combustion chamber. The baffle systemincludes a plurality of flow orifices defining a flow path for gasesgenerated by combustion of the gas generant composition, the flow pathextending between the combustion chamber and an exterior of the gasgenerating system, and a plurality of particulate aggregation surfacespositioned along the flow path of the gases for changing a flowdirection of gases impinging on the aggregation surfaces, whereinparticulates in gases impinging on the aggregation surfaces aggregate onthe surfaces.

In yet another aspect of the present invention, the present inflatorincludes an end closure that is cold-worked or otherwise compressedwithin an outer housing, the end closure containing a body bore groove,and the housing or outer tube containing a flange pressed within thegroove, thereby providing a body bore seal in a metal to metal contact.Stated another way, the present invention includes an inflator housinghaving a first end and a second end, the housing coupled to an endclosure at the first end in a metal-to-metal seal.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings illustrating embodiments of the present invention:

FIG. 1 is a cross-sectional side view of a first embodiment of a gasgenerating system in accordance with the present invention;

FIG. 1A is an enlarged view of a portion of FIG. 1 showing projected gasflow paths and projected particulate aggregation surfaces therealong;

FIG. 2 is a cross-sectional side view of a second embodiment of a gasgenerating system in accordance with the present invention;

FIG. 2A is an enlarged view of a portion of FIG. 2 showing projected gasflow paths and projected particulate aggregation surfaces therealong;and

FIG. 3 is a schematic view of an exemplary gas generating system asemployed in a vehicle occupant protection system, in accordance with thepresent invention.

FIG. 4 is a cross-sectional side view of a first embodiment of a gasgenerating system in accordance with the present invention, wherein anannular flange or flare is shown as formed about the periphery of theouter housing prior to compressing within a recessed portion or grooveformed within an end closure within the outer housing.

DETAILED DESCRIPTION

The present invention broadly comprises a gas generating system that isfabricated without the wire mesh filter required in earlier designs forremoving particulate materials from a stream of inflation gas. Thedesign utilizes a tortuous path gas flow concept to cool the gas and toretain solids in the device in order to minimize flame and particulatesfrom exiting the device. Selection of suitable gas generant compositionscapable of combusting to produce inflation gas without an undue quantityof particulates further obviates the need for a filter. Obviating theneed for a filter enables the gas generating system to be simpler,lighter, less expensive, and easier to manufacture.

FIG. 1 shows one embodiment of a gas generating system 10 in accordancewith the present invention. Gas generating system 10 is generallyconstructed of components made from a durable metal such as carbon steelor iron, but may also include components made from tough andimpact-resistant polymers, for example. One of ordinary skill in the artwill appreciate various methods of construction for the variouscomponents of the inflator. U.S. Pat. Nos. 5,035,757, 6,062,143,6,347,566, U.S. Patent Application Serial No. 2001/0045735, WO 01/08936,and WO 01/08937 exemplify typical designs for the various inflatorcomponents, and are incorporated herein by reference in their entirety,but not by way of limitation.

Referring to FIG. 1, gas generating system 10 includes a substantiallycylindrical outer housing 12 having a first end 12 a, a second end 12 bopposite the first end, and a wall 12 c extending between the ends todefine a housing interior cavity. Outer housing 12 is made from a metalor metal alloy and may be a cast, stamped, deep-drawn, extruded, orotherwise metal-formed. A nozzle 12 d is formed at housing second end 12b containing one or more gas exit orifices 12 e for enabling fluidcommunication between an interior of the housing and an associatedinflatable device (for example, an airbag or a safety belt pretensionerincorporated into a vehicle occupant protection system.) In theembodiment shown in FIG. 1, outer housing 12 and nozzle 12 d are deepdrawn as a single piece. Gas exit orifice(s) 12 e are then provided inouter housing second end 12 b by drilling, punching, or other suitablemeans.

In a particular embodiment, the gas generating system is a micro gasgenerator with outer housing 12 having an outer diameter ofapproximately 20 mm, usable in, for example, a side seat inflator or asafety belt pretensioner. However, the characteristics of theembodiments described herein may be incorporated into gas generatingsystems of many alternative sizes, usable for a variety of differentapplications.

In an alternative embodiment (not shown), the gas exit orifices may beincorporated into a gas exit manifold which is formed separately fromthe outer housing and then welded or otherwise suitably fixed to theouter housing during assembly of the gas generating system.

In another alternative embodiment (not shown), a small quantity of afilter material may be incorporated into the outer housing second endproximate the gas exit orifices to filter combustion products from theinflation fluid prior to gas distribution. Any suitable metallic meshfilter or woven wire cloth may be used, many examples of which are knownand obtainable from commercially available sources (for example, WayneWire Cloth Products, Inc. of Bloomfield Hills, Mich.)

In accordance with the present invention, and as exemplified in FIG. 4,an end closure 14 is cold-worked or otherwise metal-formed within outerhousing first end 12 a. End closure 14 has formed therealong aperipheral shoulder 14 a, a central orifice 14 b, and a peripheralcavity or recessed portion 14 c. In accordance with the presentinvention, an annular flange or protrusion 14 d of housing first end 12a (shown as a dotted line in a pre-cold-worked state in FIG. 4, and alsoshown as compressed within the groove 14 c), is drawn through a die tocold-work and thereby compress the flange within the groove 14 c. Otherknown metal-forming methods may also be employed. The diameter of theinflator may be effectively reduced by eliminating the need for atypical seal such as an o-ring at the end closure and outer housinginterface within groove 14 c, and also by compressing the annular flange14 d within groove 14 c. It will be appreciated that the volume of theannular flange or protruding portion 14 d is at least approximately orsubstantially equal to the volume defined by the groove 12 c.Accordingly, a flush metal-to-metal contact is formed at the interfaceof groove 14 c and flange 14 d once the substantially assembled inflatoris drawn and compressed through a die having a smaller diameter than theouter diameter of the annular flange 14 d prior to cold-working. Bycold-working the outer tube or housing 12 to fit within groove 14 c, thehousing 12 is compressed to provide sufficient strength in accordancewith customer specifications while simplifying the manufacturing processby reducing surface treatment or assembly of additional parts such as ano-ring. As shown in the embodiment shown in FIG. 1, the portion 14 d ofouter housing first end 12 a is pressed into peripheral cavity 14 c tosecure the end closure to outer housing 12 and at the same time providehermetic sealing of the inflator.

The cold-work technique of fitting and sealing the end closure 14 withinthe housing end 12 a results in the ability to substantially reduce thediameter of the inflator to less than one inch outer diameter, while yetretaining the structural and other design requirements surrounding theshorting clip or ignition assembly, as determined by the customer. Oneembodiment exhibits an outer diameter of approximately 20 millimeters,thereby decreasing the packaging size and also increasing the designflexibility with regard to the particular application, as a sideinflator within a seat for example.

Peripheral shoulder 14 a is configured so that an end portion a wall 16b of an ignition cup 16 (described in greater detail below) having apredetermined outer diameter may be positioned to abut shoulder 14 a.End closure 14 may be stamped, extruded, die cast, or otherwise metalformed and may be made from carbon steel or stainless steel, forexample. Although not required, if desired, an O-ring or seal (notshown) may be seated along an outer edge of end closure 14 to seal theinterface between the end closure 14 and housing wall 12 c.

Referring again to FIG. 1, an ignition cup 16 is positioned adjacent endclosure 14, and is nested within outer housing 12 for a portion of thehousing length. Ignition cup 16 has a base portion 16 a and an annularwall 16 b extending from the base portion to abut end closure 14. Baseportion 16 a and wall 16 b define a cavity 16 c for containing apyrotechnic compound 18 (for example, a known booster composition)therein. At least one ignition gas exit orifice 16 e is formed inignition cup 16 for release of ignition compound combustion productswhen ignition compound 18 is ignited. An annular recess is formed inbase portion 16 a and is dimensioned so that an end portion of anannular inner housing 22 (described below) having a predetermined innerdiameter may be positioned within the recess to aid in locating andsecuring inner housing 22 within outer housing 12. Ignition cup 16 maybe stamped, extruded, die cast, or otherwise metal formed and may bemade from carbon steel or stainless steel, for example.

In the embodiment shown in FIG. 1, a rupturable, fluid-tight seal (notshown) is positioned across ignition cup orifice 16 e to fluidly isolatecavity 16 c from a main combustion chamber 22 a formed downstream ofignition cup 16, prior to activation of the gas generating system. Theseal is secured to a face of ignition cup base portion 16 a and forms afluid-tight barrier between cavity 16 c and main combustion chamber 22a. Various known disks, foils, films, tapes, or other suitable materialsmay be used to form the seal.

Referring again to FIG. 1, a quantity of a pyrotechnic compound 18 iscontained within cavity 16 c. In the embodiment shown in FIG. 1,pyrotechnic compound 18 is a known or suitable ignition or boostercompound, whose combustion ignites a second, main gas generant charge 28positioned in combustion chamber 22 a. In an alternative embodiment,pyrotechnic compound 18 in cavity 16 c comprises the main gas generantcharge for the gas generating system. This alternative embodiment may beused in applications in which a relatively small amount of inflation gas(and, therefore, a correspondingly smaller amount of gas generant) isneeded. One or more autoignition tablets (not shown) may be placed incavity 16 c, allowing ignition of pyrotechnic compound 18 upon externalheating in a manner well-known in the art.

Referring again to FIG. 1, an igniter assembly 20 is positioned andsecured within end closure central orifice 14 b so as to enableoperative communication between cavity 16 c containing ignition compound18 and an igniter 20 a incorporated into the igniter assembly, forigniting ignition compound 18 upon activation of the gas generatingsystem. Igniter assembly 20 may be secured in central orifice 14 b usingany one of several known methods, for example, by welding, crimping,using an interference fit, or by adhesive application. An igniterassembly suitable for the application described herein may be obtainedfrom any of a variety of known sources, for example Primex Technologies,Inc. of Redmond, Wash. or Aerospace Propulsion Products by, of TheNetherlands.

The recess in ignition cup 16 is adapted to accommodate a first endportion of an inner housing 22 therealong. In the embodiment of the gasgenerating system shown in FIG. 1, inner housing 22, in combination withcenter plate 26 and bulkhead 30 (described below) define a maincombustion chamber 22 a containing a main gas generant composition 28(described in greater detail below.) Inner housing 22 is spaced apartfrom outer housing wall 12 c to form an annular gas flow passage 23extending between inner housing 22 and outer housing 12. Inner housing22 includes at least one and preferably a plurality of gas exitapertures 22 b formed therealong to enable fluid communication betweencombustion chamber 22 a and gas flow passage 23. Upon activation of thegas generating system, combustion chamber 22 a fluidly communicates withignition cup cavity 16 c by way of ignition cup orifice 16 e.

In the embodiment shown in FIG. 1, inner housing 22 telescopes or tapersdown from a first, relatively larger inner diameter enclosing centerplate 26 (described below) and combustion chamber 22 a, to a second,relatively narrower inner diameter proximate outer housing second end 12b. Thus, the width of gas flow passage 23 (defined as half of thedifference between an inner diameter of outer housing 12 and an outerdiameter of inner housing 22, where inner housing is positionedcoaxially with outer housing 12) may vary along the length of innerhousing 22. In a particular embodiment, the width of gas flow passage 23varies along the length of inner housing 22 from between a low-end valueof approximately 0.5 mm. to a high-end value of approximately 3 mm. Asecond end of inner housing 22 includes an end portion which is rolledinwardly to form an annular orifice.

Inner housing 22 also has at least one second orifice 30 d formed alongthe relatively narrow diameter portion of the inner housing to enablefluid communication between gas flow passage 23 and an interior of abaffle member 34 (described in greater detail below).

In an alternative embodiment 110 of the gas generating system (shown inFIG. 2), a second end portion of inner housing 122 is formed without thereduction in diameter and is seated along a recess formed in a baffleelement 40 (described below), thereby positioning and securing innerhousing 122 radially inwardly from outer housing 12. Thus, in thisembodiment, the width of gas flow passage 23 is substantially constantalong the length of inner housing 122. In a particular embodiment, thewidth of gas flow passage 23 is approximately 1 mm. along the length ofinner housing 22.

Inner housings 22 and 122 may be extruded, deep drawn, or otherwisemetal-formed from a metal or metal alloy.

Referring to FIG. 1, a perforate center plate 26 is press fit orotherwise suitably secured within housing 12. In the embodiment shown inFIG. 1, center plate 26 is dimensioned so as to form an interference fitwith inner housing 22 and is positioned to abut base portion 16 a ofignition cup 16. At least one orifice 26 a is provided in center plate26 to enable fluid communication between gas exit orifice 16 e inignition cup 16 and gas generant combustion chamber 22 a formed in innerhousing 22. Center plate 26 is made from a metal or metal alloy and maybe a cast, stamped, drawn, extruded, or otherwise metal-formed. Arupturable, fluid-tight seal (not shown) may be positioned acrossorifice(s) 26 a to fluidly isolate booster cavity 16 c from combustionchamber 22 a prior to activation of the gas generating system. The sealis secured to a face of center plate 26 and forms a fluid-tight barrierbetween ignition cup cavity 16 c and combustion chamber 22 a. Variousknown disks, foils, films, tapes, or other suitable materials may beused to form the seal.

Referring again to FIG. 1, gas generant composition 28 is positionedwithin combustion chambers 22 a. It has been found that the gasgenerator embodiments described herein operate most favorably with ahigh gas-yield, low solids-producing gas generant composition, such as a“smokeless” gas generant composition. Such gas generant compositions areexemplified by, but not limited to, compositions and processes describedin U.S. Pat. Nos. 6,210,505, and 5,872,329, each incorporated byreference herein. As used herein, the term “smokeless” should begenerally understood to mean such propellants as are capable ofcombustion yielding at least about 85% gaseous products, and preferablyabout 90% gaseous products, based on a total product mass; and, as acorollary, no more than about 15% solid products and, preferably, about10% solid products, based on a total product mass. U.S. Pat. No.6,210,505 discloses various high nitrogen nonazide gas compositionscomprising a nonmetal salt of triazole or tetrazole fuel, phasestabilized ammonium nitrate (PSAN) as a primary oxidizer, a metallicsecond oxidizer, and an inert component such as clay or mica. U.S. Pat.No. 5,872,329 discloses various high nitrogen nonazide gas compositionscomprising an amine salt of triazole or tetrazole fuel, and phasestabilized ammonium nitrate (PSAN) as an oxidizer.

In the embodiment shown in FIG. 1, a bulkhead or divider 30 ispress-fit, roll-crimped, or otherwise suitably secured within innerhousing 12 along the reduced-diameter portion of the inner housing, soas to maintain the divider in position within the housing when thedivider is subjected to gas pressures acting on either side of thedivider. Bulkhead 30 partitions inner housing 22 to define a chamber 30a within inner housing proximate the outer housing second end. Theportion of inner housing enclosing chamber 30 a includes apertures 30 dformed therein to enable fluid communication between gas flow passage 23and chamber 30 a. A gas tight seal is effected between divider 30 andinner housing 22, thereby preventing leakage of gas from combustionchamber 22 a toward gas exit nozzle 12 d without transiting annular gasflow passage 23, as described below. Divider 30 may be formed bystamping, casting, or any other suitable process from a metal or metalalloy.

Referring again to FIG. 1, a baffle member 34 is provided for channelinga flow of gas entering inner housing 22 from gas flow passage 23 intogas exit nozzle 12 d. Baffle member 34 includes an annular base portion34 a and an annular sleeve 34 b extending from the base portion intoinner housing 22 to define a baffle member interior in fluidcommunication with the gas flow passage 23. The baffle member interioris also in fluid communication with an interior of nozzle 12 d. Baseportion 34 a is positioned and secured between a second end portion ofinner housing 22 and outer housing gas exit nozzle 12 d to secure thebaffle member within housing 12. A rupturable, fluid-tight seal (notshown) may be positioned across an end portion of annular sleeve portion34 b to fluidly isolate inner housing end chamber 30 a from outerhousing gas exit nozzle 16 d. Various known disks, foils, films, tapes,or other suitable materials may be used to form the seal.

In an alternative embodiment (shown in FIG. 2), a baffle member 40includes a substantially circular base portion 40 a abutting innerhousing 22, and a substantially cylindrical wall 40 b extending frombase portion 40 a. Wall 40 b is in fluid communication with gas flowpassage 23. Base portion 40 a and wall 40 b combine to define a bafflechamber 40 c for receiving therein combustion products from combustionof inflation gas generant 28 in combustion chamber 22 a, in a mannerdescribed below. Baffle chamber 40 c is also in fluid communication withnozzle 12. A gas-tight seal is effected between baffle member baseportion 40 a and inner housing 22, thereby preventing leakage of gasfrom combustion chamber 22 a toward gas exit nozzle 12 d withouttransiting annular gas flow passage 23. A recess is formed in bafflemember base portion 40 a for receiving therealong the second end portionof inner housing 22, for positioning and securing the inner housingsecond end within the gas generating system. At least one (andpreferably a plurality) of orifices 40 d is formed in wall 40 b forenabling flow of combustion products received from gas flow passage 23.In the embodiment shown in FIG. 2, several orifices 40 d are spacedapart approximately 90° along a periphery of wall 40 b. A rupturable,fluid-tight seal (not shown) may positioned across an entrance to gasexit nozzle 12 d to fluidly isolate baffle chamber 40 c from outerhousing gas exit nozzle 12 d. Various known disks, foils, films, tapes,or other suitable materials may be used to form the seal.

Particulates (especially the heavier particulates) suspended in thegenerated gases will have greater momentum and dynamic inertia than thegases in which they are suspended, and do not change direction asreadily as the gases. Thus, the particulates will tend to collide withand aggregate upon surfaces along the gas flow path. It is alsodesirable to provide sufficient aggregation surface area at or near theportions of the gas generator interior where the particulates are likelyto aggregate, in order to accommodate the aggregation of particulates.In addition, the more numerous the changes in direction in the gas flow,the more opportunities are provided for aggregation of the particulates.

It is believed that the particulates are most likely to aggregate uponsurfaces on which they impinge with a relatively high velocity and/or onsurfaces which produce a relatively severe change in direction of thegas flow. In one embodiment, this is achieved by providing aggregationsurfaces oriented such that a difference between a flow direction of thegases prior to impinging on an aggregation surface and a flow directionof the gases after impinging on the aggregation surface is at leastapproximately 90°. In a particular embodiment of the present invention,each aggregation surfaces of the plurality of aggregation surfaces issubstantially perpendicular to the flow direction of the gases impingingon the respective aggregation surface. Thus, at least a portion of theparticulates striking the aggregation surfaces adhere to the surfaces,or aggregate on the surfaces, rather than changing direction with theremainder of the gas flow.

To maximize the probability of aggregating the particulates along theinternal surfaces of the gas generator, it is desirable to maximize thenumber of collisions with the internal surfaces (and thus, the number ofchanges in direction of the gases), the velocity at which theparticulates impact the internal surfaces, and the severity of changesof direction (more severe changes in gas flow direction of making itmore likely that the particulates will temporarily stop, or that theirvelocity will be drastically reduced when they impinge upon anaggregation surface).

FIG. 1A shows a projected gas flow path (indicated by arrows A) throughthe gas generating system when combustion of the gas generant begins.Referring to FIG. 1, it may be seen that orifices 22 b, 30 d, and theopening into annular sleeve 34 b define a flow path for generated gasesthrough an interior of the gas generating system to nozzle gas exitorifices 12 e. In addition, the arrangement of the various gasgenerating system components described above provides a plurality ofparticulate aggregation surfaces positioned along the flow path of thegases for changing a flow direction of gases impinging on the surfaces,so that particulates in gases impinging on the aggregation surfaces willcollect or aggregate on the surfaces.

In operation of the embodiment shown in FIGS. 1 and 1A, upon receipt ofa signal from a crash sensor, an electrical activation signal is sent toigniter 20 a. Combustion products from the igniter expand into ignitioncup cavity 16 c, igniting booster compound 18 positioned in cavity 16 c.Products from the combustion of booster compound 18 proceed out ofcavity 16 c through ignition cup orifice 16 e and into combustionchamber 22 a, igniting main gas generant 28. When the main gas generant28 has been fully ignited by the booster composition, the main gasgenerant begins to change phase from a solid to a liquid, then to a gas.

Gases and other combustion products generated by combustion of gasgenerant 28 are forced radially outward at a relatively high velocitytoward gas exit apertures 22 b by the internal pressure in inner housing22. Gases then flow through multiple orifices 22 b in inner housing 22into gas flow passage 23, charging the gas flow passage with a pressurewhich is slightly lower than the pressure within the inner housing 22.As the main gas generant burns, both P1 (internal housing pressure) andP2 (gas flow passage pressure) increase at the same rate and gases flowthrough the gas flow passage 23. Products from combustion of gasgenerant 28 proceed through inner housing gas exit apertures 22 b intoannular gas flow passage 23 and along passage 23 toward the downstreamend of inner housing 22. While a portion of the combustion products exitinner housing 22 via exit apertures 22 b, a portion of the combustionproducts also impinge on inner surfaces of inner housing 22, forcing theflow direction of the gases to change abruptly as they flow along theinner surfaces of the inner housing toward one of exit apertures 22 b.Impinging of the gases upon the inner surfaces of inner housing 22 at arelatively high velocity causes the particulates to stick to oraggregate on the inner surfaces of inner housing 22.

Similarly, particulates passing through orifices 22 b impact along innersurfaces of outer housing 12 prior to the gases changing direction asthey flow along passage 23 toward orifices 30 d. Impinging of the gasesupon the inner surfaces of outer housing 12 at a relatively highvelocity causes the particulates to stick to or aggregate on the innersurfaces of outer housing 12.

While a portion of the combustion products proceed through inner housingsecond end apertures 30 d into chamber 30 a, a portion of the combustionproducts also enter a portion 70 of the gas flow passage defined by anintersection or abutment of end portions of inner housing 22 and outerhousing 12, forcing the flow direction of the gases to change abruptlyas the gases flow back toward inner housing second end apertures 30 d.Movement of the gases into passage portion 70 at a relatively highvelocity causes the particulates to stick to or aggregate on surfaceswith passage portion 70.

Gases proceed through inner housing second end apertures 30 d intochamber 30 a. Particulates remaining in the gas stream upon enteringapertures 30 d may impact along an exterior surface of annular sleeve 34b located substantially opposite orifice(s) 30 d formed along innerhousing 22, causing the particulates to stick to or aggregate on theexterior surface of the annular sleeve.

As seen in FIG. 1A, gases deflecting off of annular sleeve 34 b areforced toward divider 30 in order to reach the hollow center portion ofthe sleeve leading to nozzle gas exit orifices 12 e. Thus, particulatesin the gases may also impact divider 30 and adhere thereto. Finally,gases proceeding toward nozzle orifices 12 e may impact an inner endsurface 12 f of the nozzle, causing particulates to adhere thereto priorto exiting of the generated gas from orifices 12 e.

As seen from the above description, a series of aggregation surfaces ispositioned between the combustion chamber and exit apertures of the gasgenerating system to impart abrupt changes in velocity to the gasstream, thereby causing particulates suspended in the gas stream toimpact the aggregation surfaces so as to adhere thereto. It is believedthat a system of aggregation surfaces as described herein acts to trapmost of the particulates produced during combustion of the gas generant,without the filter needed in other designs.

When the internal pressure in chamber 30 a reaches a predeterminedvalue, any burst seals positioned therein rupture, permitting gases toflow into the sleeve portion 34 b, proceeding out of the gas generatingsystem through nozzle 12 d.

Operation of the embodiment shown in FIGS. 2 and 2A is substantiallyidentical to that described for the embodiment shown in FIGS. 1 and 1A,with gases from gas flow passage 23 proceeding along the path defined byarrows B, flowing through openings 40 b into baffle chamber 40 c, theninto nozzle 12 d, exiting the gas generating system through gas exitorifices 12 e. While a portion of the combustion products proceedthrough inner housing second end apertures 30 d into chamber 30 a, aportion of the combustion products also enter a portion 170 of the gasflow passage defined by an intersection or abutment of end portions ofinner baffle member 40 and outer housing 12, forcing the flow directionof the gases to change abruptly as the gases flow back toward bafflemember apertures 40 d. Movement of the gases into passage portion 170 ata relatively high velocity causes the particulates to stick to oraggregate on surfaces with passage portion 170.

In the process of the gases flowing out of the propellant body, into thegas flow passage 23, into the baffle member, then out of the gas exitnozzle 12 d, all of the metal parts contacted by the gases and thetortuous path that the gases flow through provide cooling of the gases.This provides sufficient cooling of the gases so that no additionalcomponents (such as a heat sink device or a filter) are required. Inaddition, because additional cooling devices are not required, the gasesprovided by the consumed gas generant have an efficiency greater thanthose produced by existing gas generator system designs.

Referring now to FIG. 3, an embodiment of the gas generating system 10described above may also be incorporated into any of a variety ofvehicle occupant protection system elements. In one example, the 20 mmdiameter version of the gas generating system previously described isincorporated into a safety belt assembly 150 for pretensioning thesafety belt.

FIG. 3 shows a schematic diagram of one exemplary embodiment of anexemplary safety belt assembly 150. Safety belt assembly 150 includes asafety belt housing 152 and a safety belt 100 extending from housing152. A safety belt retractor mechanism 154 (for example, a spring-loadedmechanism) may be coupled to an end portion of the belt. In addition, asafety belt pretensioner 156 may be coupled to belt retractor mechanism154 to actuate the retractor mechanism in the event of a collision.Typical seat belt retractor mechanisms which may be used in conjunctionwith the safety belt embodiments of the present invention are describedin U.S. Pat. Nos. 5,743,480, 5,553,803, 5,667,161, 5,451,008, 4,558,832and 4,597,546, incorporated herein by reference. Illustrative examplesof typical gas-actuated pretensioners with which the safety beltembodiments of the present invention may be combined are described inU.S. Pat. Nos. 6,505,790 and 6,419,177, incorporated herein byreference.

Safety belt assembly 150 may also include (or be in communication with)a crash event sensor 158 (for example, an inertia sensor or anaccelerometer) operates in conjunction with a crash sensor algorithmthat signals actuation of belt pretensioner 156 via, for example,activation of igniter 20 a (not shown in FIG. 3) incorporated into thegas generating system. U.S. Pat. Nos. 6,505,790 and 6,419,177,previously incorporated herein by reference, provide illustrativeexamples of pretensioners actuated in such a manner.

Referring again to FIG. 3, safety belt assembly 150 may also beincorporated into a broader, more comprehensive vehicle occupantrestraint system 180 including additional elements such as an airbagsystem 200. Airbag system 200 includes at least one airbag 202 and a gasgenerating system 201 coupled to airbag 202 so as to enable fluidcommunication with an interior of the airbag. Airbag system 200 may alsoinclude (or be in communication with) a crash event sensor 210. Crashevent sensor 210 operates in conjunction with a known crash sensoralgorithm that signals actuation of airbag system 200 via, for example,activation of airbag gas generating system 10 in the event of acollision.

It should be appreciated that safety belt assembly 150, airbag system200, and more broadly, vehicle occupant protection system 180 exemplifybut do not limit uses of gas generating systems contemplated inaccordance with the present invention. In addition, it should beappreciated that a gas generating system incorporating a plurality ofparticulate aggregation surfaces and a high gas-yield, lowsolids-producing gas generant composition as described herein may beused in the airbag system or in other vehicle occupant protection systemelements requiring a gas generating system for operation.

In yet another aspect of the invention, a method of manufacturing aninflator may be described as follows:

-   -   1. Providing an outer housing having a first end and a second        end, and a periphery.    -   2. Forming an outer protrusion, or annular flange, about the        periphery at the first end.    -   3. Providing an end closure having a recessed portion, or a        groove.    -   4. Inserting the end closure within the outer housing at the        first end, thereby laterally aligning the outer protrusion and        the recessed portion; and    -   5. Compressing the outer protrusion within the recessed portion.        Compressing includes cold-working or otherwise metal-forming the        coupling of the protrusion and recessed portion.

An inflator and a vehicle occupant protection system containing aninflator formed by the method described above are also included. Thetext describing the end closure 14 coupled to the first end 12 a ofhousing 12, given above, is incorporated herein by reference, to fullyinform the reader of the details of this method.

It will be understood that the foregoing description of the presentinvention is for illustrative purposes only, and that the variousstructural and operational features herein disclosed are susceptible toa number of modifications, none of which departs from the spirit andscope of the present invention. The preceding description, therefore, isnot meant to limit the scope of the invention. Rather, the scope of theinvention is to be determined only by the appended claims and theirequivalents.

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 31. A gas generating system comprising: anouter housing; an inner housing positioned within the outer housing; anda baffle member contacting a portion of the inner housing to secure theportion in a position within the outer housing.
 32. The gas generatingsystem of claim 31 wherein the inner housing has a chamber formedtherein, and wherein the baffle member includes a base portion extendinginto the chamber and contacting a portion of the inner housing to securethe portion in the position.
 33. The gas generating system of claim 31wherein the inner housing has a wall, the baffle member has a recessformed therealong, and wherein the wall contacts the recess along atleast a portion thereof to secure the portion in the position.
 34. Thegas generating system of claim 31 wherein the baffle member abuts theouter housing.
 35. The gas generating system of claim 31 wherein theinner housing is spaced apart from the outer housing so as to form a gasflow passage therebetween.
 36. The gas generating system of claim 35further comprising at least one opening formed in the inner housing toenable fluid communication between an interior of the inner housing andthe gas flow passage after activation of the gas generating system; andat least one opening formed in the baffle member to enable fluidcommunication between an interior of the baffle member and the gas flowpassage after activation of the gas generating system.
 37. The gasgenerating system of claim 36 wherein a portion of the flow passageextends downstream of the at least one opening formed in the bafflemember in a direction of gas flow from the at least one opening formedin the inner housing, to define a cavity for receiving gases therein.38. The gas generating system of claim 36 further comprising at leastone gas exit opening enabling fluid communication between an interior ofthe outer housing and an exterior of the outer housing after activationof the gas generating system.
 39. The gas generating system of claim 38wherein the at least one gas exit opening is formed in a diffusercoupled to the outer housing.
 40. The gas generating system of claim 31wherein the inner housing defines a combustion chamber of the gasgenerating system, the baffle member is positioned so as to providefluid communication with the combustion chamber after activation of thegas generating system, and the baffle member contacts the portion of theinner housing so as to form a gas-tight seal therebetween.
 41. A vehicleoccupant protection system including a gas generating system inaccordance with claim
 31. 42. A gas generating system comprising: anouter housing; an inner housing positioned within the outer housing; anda baffle member coupled to the inner housing and the outer housing so asto secure the baffle member in a position within the outer housing. 43.A vehicle occupant protection system including a gas generating systemin accordance with claim
 42. 44. A gas generating system comprising: anouter housing; and a baffle member positioned within the outer housingand spaced apart from the outer housing so as to form a gas flow passagetherebetween, the baffle member having at least one opening formedtherein to enable fluid flow from a combustion chamber of the gasgenerating system into an interior of the baffle member after activationof the gas generating system, wherein a portion of the flow passageextends downstream of the at least one opening formed in the bafflemember in a direction of gas flow from the combustion chamber to the atleast one opening, to define a cavity for receiving gases therein. 45.The gas generating system of claim 44 further comprising an innerhousing positioned within the outer housing and contacting a portion ofthe inner housing to secure a portion of the inner housing in a positionwithin the outer housing.
 46. The gas generating system of claim 45wherein the inner housing defines a chamber and includes at least oneopening formed therein to enable fluid communication between the innerhousing interior and the at least one opening formed in the bafflemember after activation of the gas generating system.
 47. A vehicleoccupant protection system including a gas generating system inaccordance with claim 44.